Carbon nanotubes are an allotrope of carbon having a hollow cylindrical structure, structurally resembling a hexagonal lattice of carbon rolled into a cylinder. In addition to their mechanical properties and small size, carbon nanotubes exhibit remarkable electrical properties, providing great potential for their use in electrical and electronic applications such as sensors, semiconductor devices, displays, conductors and energy conversion devices.
Depending on their chemical structure, carbon nanotubes can be used as an alternative to organic or inorganic semiconductors as well as conductors. Specifically, carbon nanotubes exhibit either metallic or semiconductor properties depending on their chiralities.
Interest in carbon nanotubes for use as a semiconductor material for electronic applications continues to grow due to their demonstrated carrier mobilities being magnitudes higher than silicon.
Indeed, carbon nanotubes represent an emerging research area. In addition to their applications to field effect transistors (FETs), organic solar cells, sensors, and energy conversion devices such as fuel cells, carbon nanotubes can be applicable to a variety of materials including composites (polymer and cement), fire-retardant materials, and UV-protecting textile and filters.
In order to make devices out of nanotubes, it is important to be able to manipulate the nanotubes in a controlled way. For example, transistors are the basic building blocks of integrated circuits. Therefore, research has been conducted to make transistors from carbon nanotubes. Multi-wall and single-wall nanotubes have been used as the channel of a FET with single-walled nanotubes being more popular in the present designs due to their electric properties.
One approach to the formation of large scale multilayer structures of single-walled nanotubes (SWNTs) on a variety of substrates involves the guided growth of aligned arrays or random networks on a growth substrate and then the physical transfer of the nanotubes in multiple, sequential steps onto a target substrate. Presently, a double transfer of SWNTs onto a target substrate has been demonstrated. However, research continues in order to provide improved techniques that are suitable for more than two transfers onto a target substrate. Accordingly, there exists a need in the art for wafer-scale multiple transfer of carbon nanotubes from a source substrate to a target substrate.